Imagine if you went to your creative (John) with this feedback from your client (Kelly):
You: Hi John, I've received some feedback, from Kelly, about the brochure design. We've got to make a lot of changes, unfortunately.
John: Oh, really? I thought we nailed the brief! What did Kelly say?
You: I've marked up the proof with the text alterations, and we have to move a couple of things around. In terms of the overall design, Kelly said she doesn't like it.
John: Doesn't like it? What did she mean?
You: I don't know, she just said she doesn't like it, so can you please have another go at the design?
One of the quickest ways to have a time blowout on a job is via revision cycles. Hopefully you will always protect yourself at the quote stage (e.g. "this quote covers two sets of author's alterations. Additional author's alterations will be charged at $x per hour..."), but that only covers AUTHOR'S alterations. What happens if the error is deemed to be the fault of the agency? In the scenario, above, the request for a change to the text is an "author's alteration", but the request for a change to the design would have to be absorbed as an internal cost, as you have not yet satisfied the initial design brief. You need to keep these types of non-chargeable alterations to a minimum.
It can be difficult for a client to articulate why they don't like something, but it’s imperative that you ask enough questions to uncover exactly what is bothering them. If you don’t, any subsequent work could be a waste of agency time and profit, and would be like taking shots in the dark (not to mention you would end up with a very frustrated internal team).
The key is always to glean ACTIONABLE feedback - something that will give your creatives clear direction to follow. It may be that your client doesn't like a particular colour, or font, or finds the typeface too small to read. Maybe she feels that you haven't captured the personality of the brand as well as she had hoped; or maybe the design reminds her of a movie she disliked as a child. By uncovering your client’s likes and dislikes you’ll be able to rectify the current design and remember these preferences for future projects.